1. Field of the Invention
The invention relates to a series/parallel/series shift register memory comprising a substrate on which there are provided storage positions for the storage of a data element which is represented in a multivalent, single, physical quantity in each storage position, said shift register memory comprising a serial data input for electric signals, a converter for converting a signal received into the representation of a data element, a series input register which is connected to the converter and which comprises n&gt;1 switch positions, a number of n single storage registers each of which is connected to a switch position and which comprise at least two storage positions in order to form a parallel storage register, a series output register which is n-fold connected to the parallel storage register by way of a relevant second switch position and which comprises a serial data output, said shift register memory comprising a transfer control device for transferring, after the reception of n data representations in the series input register, these representations in parallel to the parallel storage register in a recurrent manner and for presenting a corresponding number of data representations from the parallel storage register to the series output register, said transfer control device otherwise activating only the series input/output registers, said transfer control device also serving to ignore single storage registers which have been indicated as being faulty on the basis of one or more fault indicators stored in an indicator memory, and to conduct the relevant data representations for each indicated single storage register via a relevant first redundant, single storage register.
2. Description of the Prior Art
In one known such shift a register memory described in U.S. Pat. No. 4,155,121 each physical quantity is an electric charge stored in an integrated capacitor, which charge is advanced in steps by electric drive signals; such memories are so-called charge coupled devices which are a subcategory of charge transfer devices. The data elements may be discrete and bivalent, discrete and multivalent or even analog. In another known such shift register memory described in U.S. Pat. No. 4,073,012 the physical quantity is a local magnetization in a ferrimagnetic substrate, i.e. a magnetic bubble. The magnetic bubbles can be driven by a magnetic field which rotates in the plane of the substrate, by energizing current conductors provided on the substrate or in another way. The data elements are usually (but not exclusively) discrete and bivalent. During the manufacture of such memories faults occur, these being usually located in the comparatively large area in which the single storage registers are situated. The yield of the manufacturing process can be increased by providing extra and therefore nominally redundant single storage registers which, if one or more faulty single storage registers occur, are used instead. The detection of faulty storage registers may take place during manufacture. During its manufacture and prior to the assembly of the substrate with the memory in a memory system, however, such a memory is volatile so that an expensive bookkeeping system is necessary in order to obtain an up-to-date record of the fault locations in each shift register memory during the successive manufacturing steps. These locations may differ from one memory to another. Moreover, additional problems may arise because (further) single storage registers could become faulty during operation.